Radiative Thermal Management in Face Masks with a Micro/Nanofibrous Filter.

Micro/nanofiber-based face masks are recommended as personal protective equipment (PPE) against particulate matter (PM), especially PM0.3. Ensuring thermal comfort in daily use face masks is essential in many situations. Here, radiative thermal management is introduced into face masks to elevate the user comfort. An interlayered poly(lactic acid) (PLA) micro/nanofibrous filter effectively captures PM0.3 (99.69%) with minimal pressure drop (49 Pa). Thermal regulation is accomplished by controlling the mid-infrared (MIR) emissivity of the face mask's outer surface. Cooling face masks feature cotton nonwovens with high MIR emissivity (90.7%) for heat dissipation, while warming face masks utilize perforated Al/PE films with minimal MIR emissivity (10.7%) for warmth retention. Skin temperature measurements indicate that the skin covered by the cooling face mask could be 1.1 °C lower than that covered by the 3M face mask, while the skin covered by the warming face mask could be 1.3 °C higher than that covered by the 3M face mask.

Experimental and Numerical Investigation of Slip Effect on Nanofiber Filter Performance at Low Pressures.

Nanofiber filters are widely used in air filtration applications due to their superior performance over microfiber filters. Velocity slip around nanofibers has been identified as a key factor contributing to their high figure of merit, yet its impact on filter performance, especially particle collection efficiency, remains unclear due to the difficulty in isolating the slip effect as the sole variable. This study combines experimental and simulation methods to investigate the slip effect by adjusting the air molecule mean free path, rather than varying fiber size as done in previous studies. Filter media with mean fiber sizes ranging from 16.2 to 0.084 µm are utilized. An image-based regression method is developed to address the challenge of determining the solidity of thin nanofiber layers. The results show that the slip effect is enhanced as the testing pressure decreases, reducing pressure drop by less than 15% for microfiber filters and over 50% for nanofiber filters ≈100 nm. The enhanced slip effect at low pressures (i.e., relatively low pressure compared to the ambient environment) significantly improves filtration efficiency, especially for particles larger than 100 nm. It also proposes semi-empirical equations for predicting filter performance in slip and transition flow regimes.

Biodegradable Poly (L-Lactic acid) Fibrous Membrane with Ribbon-Structured Fibers and Ultrafine Nanofibers Enhances Air Filtration Performance.

Here, the poly (l-lactic acid) (PLLA) membrane with multi-structured networks (MSN) is successfully prepared by electrospinning technology for the first time. It is composed of micron-sized ribbon-structured fibers and ultrafine nanofibers with a diameter of tens of nanometers, and they are connected to form the new network structure. Thanks to the special fiber morphology and structure, the interception and electrostatic adsorption ability for against atmospheric particulate matter (PM) are significantly enhanced, and the resistance to airflow is reduced due to the "slip effect" caused by ultrafine nanofibers. The PLLA MSN membrane shows excellent filtration performance with ultra-high filtration efficiency (>99.9% for PM2.5 and >99.5% for PM0.3) and ultra-low pressure drop (≈20 Pa). It has demonstrated filtration performance that even exceeds current non-biodegradable polymer materials, laying the foundation for future applications of biodegradable PLLA in the field of air filtration. In addition, this new structure also provides a new idea for optimizing the performance of other polymer materials.

Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration.

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447 nm, branched fiber of 24.7 nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26 µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4 Pa) and a quality factor up to 0.083 Pa-1 on a 40 µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.

Urban meadow-a recipe for long-lasting anti-smog land cover.

This study evaluates for the first time whether 33 species of annual and perennial herbaceous plants originating from a moderate climate continue to be capable of air filtration of particulate matter (PM) at the end of the growing season. Research was undertaken in November in two urban meadows located in trafficked areas of Bialystok (Poland). The study reveals that despite the lateness in the season, tested species remained capable of PM accumulation. Deposition of total PM exceeding 100 µg·cm-2 was found on S. vulgaris, S. latifolia, T. pratense, E. vulgare, and A. officinalis. The finest and most toxic fraction was accumulated most effectively by S. latifolia, E. vulgare, and L. vulgare (>12 µg·cm-2). Taraxacum officinale and M. sylvestris retained c. 60% of PM in their epicuticular wax. A slight significant correlation was found between rosette growth pattern and deposition of total PM on foliage, while the accumulation of the finest fraction was correlated with a simple leaf shape. These results support the usefulness of urban meadows as long-lasting air bio-filters provided that their composition includes species that have a confirmed, prolonged PM accumulation capacity and that the meadow is not mown in autumn.

This is the first time that the PM accumulation capacity of urban meadow species at the end of the vegetative season has been evaluated in real-life conditions. Evidence of prolonged PM deposition on herbaceous plants was obtained. To enhance PM mitigation in cities located in moderate climate zones, it is proposed that a selection of species be sown in urban meadows.

Resilient and Antipuncturing Si3N4 Nanofiber Sponge.

Ceramic nanofibrous nanostructure-based sponges have attracted significant attention due to ultrahigh porosity, low thermal conductivity, large specific area, and chemical stability. From the regulation of the fiber itself to the construction method of 3D networks, efforts are being made to improve the mechanical properties of ceramic sponges for practical applications. So far resilient compressibility has been realized in ceramic nanofibrous-based sponges via structural design, but they still show brittle fracture under a more complex stress state. Herein, we introduced a highly aligned and interwoven Si3N4 nanofiber sponge, which exhibits superflexibility, large break elongation (>80%), large-strain reversible stretch (20%), and good resistance to tensile fatigue. The ceramic sponge also displays reversible compressibility up to 60% strain, puncture resistance, high air filtration efficiency (>99.8%), and low pressure drop (38% of cotton fiber), making the ceramic sponge a high-performance wearable respirator to protect us from harm due to PM2.5 pollution and possible microorganisms.

Two-Dimensional Nanofibrous Networks by Superspreading-Based Phase Inversion for High-Efficiency Separation.

Two-dimensional (2D) nanomaterials have been widely applied as building blocks of nanoporous materials for high-precision separations. However, most existing 2D nanomaterials suffer from poor continuity and a lack of interior linking, resulting in deteriorated performance when assembled into macroscopic bulk structures. Here, a unique superspreading-based phase inversion technique is proposed to directly construct 2D nanofibrous networks (NFNs) from a polymer solution. By tailoring capillary behavior, polymer solution droplets evolve into ultrathin liquid films through superspreading; manipulating phase instability, subsequently, enables the liquid film to phase invert into continuous nanostructured networks. The assembled single-layered NFNs possess integrated structural superiorities of 1D nanoscale fiber diameter (∼40 nm) and 2D lateral infinity, exhibiting a weblike nanoarchitecture with extremely small through-pores (∼100 nm). Our NFNs show remarkable performances in air filtration (PM0.3 removal) and water purification (microfiltration level). This creation of such attractive 2D fibrous nanomaterials can pave the way for versatile high-performance separation applications.

Multifactorial evaluation of an ultra-fast process for electrospinning of recycled expanded polystyrene to manufacture high-efficiency membranes for nanoparticle air filtration.

The increased production of polystyrene waste has led to the need to find efficient ways to dispose of it. One possibility is the use of solid waste to produce filter media by the electrospinning technique. The aim of this work was to develop an ultra-fast electrospinning process applied to recycled polystyrene, with statistical evaluation of the influence of polymeric solution parameters (polymer concentration and percentage of DL-limonene) and process variables (flow rate, voltage, and type of support) on nanoparticle collection efficiency, air permeability, and fiber diameter. An extensive characterization of the materials and evaluation of the morphology of the fibers was also carried out. It was found that recycled expanded polystyrene could be used in electrospinning to produce polymeric membranes. The optimized condition that resulted in the highest nanoparticle collection efficiency was a polymer concentration of 13.5%, percentage of DL-limonene of 50%, voltage of 25 kV, and flow rate of 1.2 mL/h, resulting in values of 99.97 ± 0.01%, 2.6 ± 0.5 × 10-13 m2, 0.19 Pa-1, and 708 ± 176 nm for the collection efficiency of nanoparticles in the range from 6.38 to 232.9 nm, permeability, quality factor, and mean fiber diameter, respectively. All the parameters were found to influence collection efficiency and fiber diameter. The use of DL-limonene, a natural solvent, provided benefits including increased collection efficiency and decreased fiber size. In addition, the electrostatic filtration mechanism was evaluated using the presence of a copper grid as a support for the nanofibers. The findings demonstrated that an electrospinning time of only 5 min was sufficient to obtain filters with high collection efficiencies and low pressure drops, opening perspectives for the application of polystyrene waste in the development of materials with excellent characteristics for application in the area of atmospheric pollution mitigation.

Health benefits to vulnerable populations by meeting particle-level guidelines inside schools with different ventilation conditions.

We conducted simultaneous real-time measurements for particles on the premises of four schools, two of which were naturally ventilated (NV) and two mechanically ventilated (MV) in Kanpur, India. Health to school children from reduced particle levels inside classrooms simulated to the lowest acceptable levels (ISHRAE Class C: PM10 ≤ 100 µg/m3 & PM2.5 ≤ 25 µg/m3) using air filters were examined. Lung deposition of particles was used as a proxy for health impacts and calculated using the MPPD model. The particle levels in all classrooms were above the baseline, with NV classrooms having higher particle masses than MV classrooms: 72.16% for PM1, 74.66% for PM2.5, and 85.17% for PM10. Our calculation reveals a whooping reduction in particles deposited in the lungs (1512% for PM10 and 1485% for PM2.5) in the case of the NV classrooms. Results highlight unhealthy air inside classrooms and suggest urgent interventions, such as simple filtration techniques, to achieve acceptable levels of particles inside schools.

Multi-Unit Needleless Electrospinning for One-Step Construction of 3D Waterproof MF-PVA Nanofibrous Membranes as High-Performance Air Filters.

The airborne particulate matter (PM) seriously threatens people's health. Personal protective equipment with electrospun nanofibers is an effective method to make people away from air pollutants. Herein, 3D waterproof melamine-formaldehyde polyvinyl alcohol (MF-PVA) nanofibrous membranes are fabricated by a one-step method combining multi-unit needleless electrospinning and a thermal treatment device in a line. 3D nanofibrous structures can be controlled by adjusting the solution concentration of each unit. The PVA nanofibrous membranes become waterproof after cross-linking with MF resin in the following thermal treatment device. The optimized MF-PVA nanofibrous membrane shows excellent air filtration performance (97.3% for PM0.3 , 100% for PM1.0 , and 100% for PM2.5 ) and low air resistance (76 Pa). These 3D waterproof MF-PVA nanofibrous membranes exhibit ultra-stable performance in various practical environments.

Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review.

Installation of technologies to remove or deactivate respiratory pathogens from indoor air is a plausible non-pharmaceutical infectious disease control strategy. OBJECTIVE: We undertook a systematic review of worldwide observational and experimental studies, published 1970-2022, to synthesise evidence about the effectiveness of suitable indoor air treatment technologies to prevent respiratory or gastrointestinal infections. METHODS: We searched for data about infection and symptom outcomes for persons who spent minimum 20 h/week in shared indoor spaces subjected to air treatment strategies hypothesised to change risk of respiratory or gastrointestinal infections or symptoms. RESULTS: Pooled data from 32 included studies suggested no net benefits of air treatment technologies for symptom severity or symptom presence, in absence of confirmed infection. Infection incidence was lower in three cohort studies for persons exposed to high efficiency particulate air filtration (RR 0.4, 95%CI 0.28-0.58, p < 0.001) and in one cohort study that combined ionisers with electrostatic nano filtration (RR 0.08, 95%CI 0.01-0.60, p = 0.01); other types of air treatment technologies and air treatment in other study designs were not strongly linked to fewer infections. The infection outcome data exhibited strong publication bias. CONCLUSIONS: Although environmental and surface samples are reduced after air treatment by several air treatment strategies, especially germicidal lights and high efficiency particulate air filtration, robust evidence has yet to emerge that these technologies are effective at reducing respiratory or gastrointestinal infections in real world settings. Data from several randomised trials have yet to report and will be welcome to the evidence base.

Dual-bionic nano-groove structured nanofibers for breathable and moisture-wicking protective respirators.

Coronavirus disease 2019 (COVID-19) pandemic makes protective respirators highly demanded. The respirator materials should filter out viral fine aerosols effectively, allow airflow to pass through easily, and wick away the exhalant moisture timely. However, the commonly used melt-blown nonwovens perform poorly in meeting these requirements simultaneously. Herein, dual-bionic nano-groove structured (NGS) nanofibers are fabricated to serve as protective, breathable and moisture-wicking respirator materials. The creativity of this design is that the tailoring of dual-bionic nano-groove structure, combined with the strong polarity and hydrophilicity of electrospinning polymer, not only endows the nanofibrous materials with improved particle capture ability but also enable them to wick away and transmit breathing moisture. Benefitting from the synthetic effect of hierarchical structure and the intrinsic property of polymers, the resulting NGS nanofibrous membranes show a high filtration efficiency of 99.96%, a low pressure drop of 110 Pa, and a high moisture transmission rate of 5.67 kg m-2 d-1 at the same time. More importantly, the sharp increase of breathing resistance caused by the condensation of exhaled moisture is avoided, overcoming the bottleneck faced by traditional nonwovens and paving a new way for developing protective respirators with high wear comfortability.

Electrospun PVB/AVE NMs as mask filter layer for win-win effects of filtration and antibacterial activity.

The COVID-19 pandemic has caused serious social and public health problems. In the field of personal protection, the facial masks can prevent infectious respiratory diseases, safeguard human health, and promote public safety. Herein, we focused on preparing a core filter layer for masks using electrospun polyvinyl butyral/apocynum venetum extract nanofibrous membranes (PVB/AVE NMs), with durable interception efficiency and antibacterial properties. In the spinning solution, AVE acted as a salt to improve electrical conductivity, and achieve long-lasting interception efficiency with adjustable pore size. It also played the role of an antibacterial agent in PVB/AVE NMs to achieve win-win effects. The hydrophobicity of PVB-AVE-6% was 120.9° whereas its filterability reached 98.3% when the pressure drop resistance was 142 Pa. PVB-AVE-6% exhibited intriguing properties with great antibacterial rates of 99.38% and 98.96% against S. aureus and E. coli, respectively. After a prolonged usability test of 8 h, the filtration efficiency of the PVB/AVE masks remained stable at over 97.7%. Furthermore, the antibacterial rates of the PVB/AVE masks on S. aureus and E. coli were 96.87% and 96.20% respectively, after using for 2 d. These results indicate that PVB/AVE NMs improve the protective performance of ordinary disposable masks, which has certain application in air filtration.

Silk fibroin fibers-based shape memory membrane with Janus wettability for multitiered wearable protection.

Realizing breathable shape memory fiber-based material with antibacterial and waterproof performances is important for multitiered wearable protection to address the increasing concerns of air pollution. Herein, using an alternating electrospinning-electrospraying technology, we develop a fiber-based membrane with Janus wettability based on a silk fibroin nanofibers-substrate (SFNFs), a polyurethane nanospheres-top layer (PUNSs), and a middle layer of PU nanofibers-mat with in-situ grown silver nanoparticles (PUNFs-AgNPs), which serves separately for skin contact, a self-cleaning physical barrier to resist external aerosol/bacteria (PM2.5 filtration efficiency ~ 98.1%), and a bio-barrier that can sterilize harmful particles and inhibit bacteria proliferation (> 95%). This breathable Janus film (SFNFs/PUNFs-AgNPs/PUNSs, SPAP) with an antibacterial filter shows shape memory stretchability enabled by the thermoplastic PU component, which is mechanically adaptive to human body for wearable protection. This work presents a breathable wearable material for air-filtration and anti-bacteria, promising for applications such as wound dressings, medical masks, protection suits, and multifunctional filters. Graphical abstract: An alternating electrospinning-electrospraying technology was proposed to achieve a silk fibroin-based antibacterial membrane with Janus wettability, as well as good skin affinity and breathability, which serves well as physical and bio-barriers for water resistance, PM2.5 filtration (~98.1%) and bacteria inhibition (efficiency of 95%). This shape memory Janus membrane can adapt mechanically to human body curvatures for functional wearable protections. Supplementary Information: The online version contains supplementary material available at 10.1557/s43578-022-00805-w.

Neutropenia-related aspergillosis in non-transplant haematological patients hospitalised under ambient air versus purified air conditions.

BACKGROUND: To reduce the risk of invasive aspergillosis (IA), air purification by high-efficiency particulate air filtration and laminar air flow (HEPA/LAF) is standard of care in allogeneic blood stem cell transplantation. Its use in non-transplant haematological patients is inconsistent. OBJECTIVES: We sought to assess the incidence and outcome of pulmonary IA in non-transplant patients with life-threatening neutropenia by comparing an ambient air hospitalisation period (2008-2011) with a subsequent HEPA/LAF hospitalisation period (2012-2014). PATIENTS AND METHODS: We compared 204 consecutive patients with acute myeloid leukaemia, acute lymphoblastic leukaemia or aplastic anaemia completing 534 neutropenia-related hospitalisations under ambient air conditions with 126 such patients completing 437 neutropenia-related hospitalisations under HEPA/LAF conditions. IA was defined using the 2008 EORTC/MSG criteria. RESULTS: Within a 7-year study period, we observed one 'proven', three 'probable' and 73 'possible' IAs, most often during acute leukaemia remission induction. Their frequency rose with increasing duration of life-threatening neutropenia (1-10 days, 1.8%; >40 days, 35.2%) and concomitant severe anaemia (0 days, 3.2%; >20 days, 31.0%). Multiple logistic regression revealed a strong correlation between IA incidence and hospitalisation under HEPA/LAF conditions (odds ratio [OR], 0.368 [95% confidence interval, 0.207-0.654]; p < .001) and duration of neutropenia (OR, 1.043 [1.023-1.062] per day; p < .001) and anaemia (OR, 1.044 [1.008-1.081] per day; p = .016). IA-associated fatal outcomes were non-significantly reduced under HEPA/LAF (OR, 0.077 [0.005-1.151]; p = .063). The protective effect of HEPA/LAF was not seen under posaconazole prophylaxis (OR, 0.856 [0.376-1.950]; p = .711). CONCLUSIONS: Implementation of HEPA/LAF was associated with a significant reduction in neutropenia-related IA in non-transplant haematological patients.

An Optimized Active Sampling Procedure for Aerobiological DNA Studies.

The Earth's atmosphere plays a critical role in transporting and dispersing biological aerosols. Nevertheless, the amount of microbial biomass in suspension in the air is so low that it is extremely difficult to monitor the changes over time in these communities. Real-time genomic studies can provide a sensitive and rapid method for monitoring changes in the composition of bioaerosols. However, the low abundance of deoxyribose nucleic acid (DNA) and proteins in the atmosphere, which is of the order of the contamination produced by operators and instruments, poses a challenge for the sampling process and the analyte extraction. In this study, we designed an optimized, portable, closed bioaerosol sampler based on membrane filters using commercial off-the-shelf components, demonstrating its end-to-end operation. This sampler can operate autonomously outdoors for a prolonged time, capturing ambient bioaerosols and avoiding user contamination. We first performed a comparative analysis in a controlled environment to select the optimal active membrane filter based on its ability to capture and extract DNA. We have designed a bioaerosol chamber for this purpose and tested three commercial DNA extraction kits. The bioaerosol sampler was tested outdoors in a representative environment and run for 24 h at 150 L/min. Our methodology suggests that a 0.22-µm polyether sulfone (PES) membrane filter can recover up to 4 ng of DNA in this period, sufficient for genomic applications. This system, along with the robust extraction protocol, can be automated for continuous environmental monitoring to gain insights into the time evolution of microbial communities within the air.

Transparent Air Filters with Active Thermal Sterilization.

The worldwide proliferation of COVID-19 poses the urgent need for sterilizable and transparent air filters to inhibit virus transmission while retaining ease of communication. Here, we introduce copper nanowires to fabricate transparent and self-sterilizable air filters. Copper nanowire air filter (CNAF) allowed visible light penetration, thereby can exhibit facial expressions, helpful for better communication. CNAF effectively captured particulate matter (PM) by mechanical and electrostatic filtration mechanisms. The temperature of CNAF could be controlled by Joule-heating up to 100 °C with thermal stability. CNAF successfully inhibited the growth of E. coli because of the oligodynamic effect of copper. With heat sterilization, the antibacterial efficiency against G. anodireducens was greatly improved up to 99.3% within 10 min. CNAF showed high reusability with stable filtration efficiency and thermal antibacterial efficacy after five repeated uses. Our result suggests an alternative form of active antimicrobial air filter in preparation for the current and future pandemic situations.

Mass Production of Hierarchically Designed Engine-Intake Air Filters by Multinozzle Electroblow Spinning.

Particulate matter damages engines of vehicles when blown into the ventilation system. Conventional engine-intake filter is cellulose microfiber board with an average diameter larger than ten microns, which has low removal efficiency of ultrafine particular matter. In this work, we apply ultrafine polyurethane nanofibers (∼122.8 nm) onto pleated cellulose board using scalable multinozzle electroblow spinning technology, which improves filtration efficiency of particulate matter with a diameter of less than 0.3 µm PM0.3 greatly. The thermoplastic polyurethane 85A nanofiber membranes are transparent, and display superior filtration performance which meets up with the 95% filtration efficiency standard in GB 19083-2010 technical requirements for protective face mask for medical use. The lightweight pleated thermoplastic polyurethane/cellulose composites intercept ∼90% ultrafine PM0.3 under airflow velocity of 32 L min-1 and possess great resistance to shock. These hierarchically designed filters follow a mechanical mechanism and can be used in on-road and off-road cars in the long run.

Fit-Tested N95 Masks Combined With Portable High-Efficiency Particulate Air Filtration Can Protect Against High Aerosolized Viral Loads Over Prolonged Periods at Close Range.

BACKGROUND: Healthcare workers (HCWs) are at risk from aerosol transmission of severe acute respiratory syndrome coronavirus 2. The aims of this study were to (1) quantify the protection provided by masks (surgical, fit-testFAILED N95, fit-testPASSED N95) and personal protective equipment (PPE), and (2) determine if a portable high-efficiency particulate air (HEPA) filter can enhance the benefit of PPE. METHODS: Virus aerosol exposure experiments using bacteriophage PhiX174 were performed. An HCW wearing PPE (mask, gloves, gown, face shield) was exposed to nebulized viruses (108 copies/mL) for 40 minutes in a sealed clinical room. Virus exposure was quantified via skin swabs applied to the face, nostrils, forearms, neck, and forehead. Experiments were repeated with a HEPA filter (13.4 volume-filtrations/hour). RESULTS: Significant virus counts were detected on the face while the participants were wearing either surgical or N95 masks. Only the fit-testPASSED N95 resulted in lower virus counts compared to control (P = .007). Nasal swabs demonstrated high virus exposure, which was not mitigated by the surgical/fit-testFAILED N95 masks, although there was a trend for the fit-testPASSED N95 mask to reduce virus counts (P = .058). HEPA filtration reduced virus to near-zero levels when combined with fit-testPASSED N95 mask, gloves, gown, and face shield. CONCLUSIONS: N95 masks that have passed a quantitative fit-test combined with HEPA filtration protects against high virus aerosol loads at close range and for prolonged periods of time.

The Removal of Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Other Microbial Bioaerosols by Air Filtration on Coronavirus Disease 2019 (COVID-19) Surge Units.

Airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detected in a coronavirus disease 19 (COVID-19) ward before activation of HEPA-air filtration but not during filter operation; SARS-CoV-2 was again detected following filter deactivation. Airborne SARS-CoV-2 was infrequently detected in a COVID-19 intensive care unit. Bioaerosol was also effectively filtered.